The objective of this protocol is to learn where blood VLDL-triglycerides come from after an overnight fast and how this is altered in diabetic and non-diabetic hypertriglyceridemia. The metabolic contributions to VLDL-triglyceride from circulating free fatty acids derived from adipose fat during the fast, from preceding meals stored in the liver, from the preceding days' free fatty acids stored in the liver after meals, and from de novo synthesis will be measured using stable isotopes. Subjects will be fed controlled diets for 4 weeks then enter the GCRC for 4 days for isotope administration, collection of blood samples, and for consumption of all meals.